Organo substituted silicon polymers and method of making them



Patented sen. i949 ORGANG SUBSTITUTED-SILICON POLYMERS AND METHOD OFMAKING THEM James Franklin Hyde, Corning, N. Y., asslgnor to CorningGlass Works, Corning, N. Y., a corporation of New York No Drawing.Application May 27, 1946, Serial No. 672,695

2 Claims. Cl. 260-4482) This application is a continuation-in-part of mycopending application Serial Number 432,528, filed February 26, 1942,and Serial Number 514,410, filed December 15, 1943, now Patent2,457,677, which applications disclose all the subject matter hereof.This invention relates to the products obtained by the hydrolysis anddehydration of organosilicanes.

The hydrolysis of a silicane of the type SiX4, where X is anyhydrolyzable atom or group, such as halogen, alkoxy, hydrogen, etc.,does not result in a simple hydroxy compound but produces instead abrittle, insoluble, infusible gel comprising a three-dimensional networkof structural units composed of siloxane linkages as a result of theconcurrent or subsequent loss of water from the intermediately formedhydroxy compound,

The formation of a. siloxane linkage requires the close approach of twohydroxyl groups. It is apparent that, in thfiormation of such a rigidstructure, many hydroxyl groups become isolated and block some of thepossible cross linkages. As the structural network becomes morecomplicated, dehydration becomes increasingly more dimcult, and theresult is a partially dehydrated silica gel of poor dimensionalstability.

Organo substituted sillcanes of the type RSiXa are prepared by means ofthe well known Grignard reaction, where R may be any organic radicalwhich is capable of reacting with magnesium to form a Grignard reagentand which is attached to silicon through a carbon atom. Such organosubstituted sllicanes are also hydrolyzed on treatment with water,although the reaction is less vigorous than in the case of theunsubstituted silicane under comparable conditions.

x OH R-si-x 11-41-03 R-s 1-o H Here it will be seen that in eachstructural unit one of the four silicon bonds is blocked by the organicradical R, and only three siloxane linkages can form. Such compounds arestill capable of three-dimensional polymerization.

The chemical and structural changes occurring in this type ofsubstituted silicanesare the same as those described above in theformation of silica gel. The chief distinction arises from the fact thatthe property of solubility in organic solvents, particularly in thelower stages of condensation, is acquired due to the presence of theorganic radical. The tendency of intermediate partially dehydratedproducts to further dehydrate is also decreased. The latter tendency ismore noticeable with increasing size of the radical. As the stage ofessentially complete dehydration is approached, the mono-substitutedproducts, which in reality are substituted silica gels, lose theirsolubility and become hard and brittle. However, there is a markedimprovement in dimensional stability over silica gel.

On substituting a second organicradical, which is attached to siliconthrough a carbon atom and which may or may not be different from thefirst, a silicane of the type RR'SiXz results. Such compounds also maybe hydrolyzed and dehydrated, the dehydration probably proceeding tosome extent concurrently with the hydrolysis, particularly if thetemperature is allowed to rise.

In each structural unit two of the four silicon bonds are now blocked bythe organic radical R and R, and only two siloxane linkages arepossible. Hence a three-dimensional network is no longer possible andthe resulting organo-siloxanes can comprise only chain and cyclicstructures. Intermediate crystalline de-hydroxy compounds can in someinstances be isolated. The final products which are usually resinous incharacter bear little physical resemblance to silica gel but are closelyrelated thereto in chemical structure, difiering only in the restrictionof possible siloxane linkages.

Organo substituted silicanes of the type RR'R"S1X, when hydrolyzed anddehydrated,

yield very simple oxides in the structural unit of which three of thefour silicon bonds are blocked by the organic radicals R, R and R".

In this case, ease of hydrolysis is further diminished and in some casesthe intermediate hydroxy silicanes can be isolated. The completelydehydrated product is dimeric because only one siloxane linkage can beformed. The dimers are either crystalline or liquid.

Prior attempts to utilize the above described reactions have notcontemplated combinations thereof, but have been confined more or lessto the individual reactions and their products. Such products, as shownabove, have limited utility and the range of properties obtainable inthe products of a given type of reaction is relatively restricted. Forexample, the product resulting from Type I reaction is an insoluble,infusible gel of little utility; Type IV reaction yields generally inertliquid products which, although they are soluble in organic solvents,cannot be polymerized beyond the dimer and hence cannot be utilized perse for coating compositions, resinous impregnants and the like.

An object of this invention is the production of new and useful productsfrom these reactions which will have desirable predetermined properties.

Another object is to combine the above described reactions and thus tointer-condense .the hydrolysis products of a plurality of substitutedand unsubstituted organo silicanes.

Another object is to produce liquid products of varying viscosity.

The new method comprises mixing predetermined quantities of two or morecompounds of the types, SiXi, RSiXs, Eli/Sim, and RR'R"SiX,

where R, R and R" are the same or different organic radicals and X isany hydrolyzable atom or group, or two or more compounds of any one ofthese types, except Type I, the organic radical or radicals beingdifferent for each compound, and causing them to hydrolyze together andto become inter-condensed. This is best accomplished by introducing intothe mixture by dropwise addition thereto the amount of water which iscalculated for complete hydrolysis of the mixture and which preferablyis dissolved in from two to four volumes of a common solvent such asalcohol,

dioxan, acetic acid, acetone, etc. Although a difference in thereactivity of the various individual types of hydrolyzable compounds anda variation in the amounts present in the initial mixture may make itdesirable to vary the conditions or the process, as will appear from aconsideration of the accompanying examples, the above recited procedurein general is to be preferred. The use of a water miscible solvent fordiluting the hydrolyzable mixture or the water or both and the dropwiseaddition of the water insures the maintenance of homogeneity duringhydrolysis. Under these conditions condensation or the formation ofsiloxane linkages occurs concurrently with the hydrolysis, but it is tobe understood that the extent of further subsequent dehydration lsoptional and will depend largely upon the use to which the product willbe put.

In any hydrolyzable silicanes, one or more of which is organosubstituted through C-Si linkage and contains on the average from one totwo hydrolyzable atoms or groups attached to the silicon atom,co-hydrolysisand dehydration by this method will result ininter-condensation or formation of interconnecting oxygen linkagesbetween the silicon atoms of the various silicanes. The variety of thesubstituted organic radicals is limited only by their ability to form aGrignard reagent. In other words, the organo silicanes which may beemployed in my process include all such compounds which contain one ormore bydrolyzable atoms or groups and which may be prepared by means ofthe well-known Grignard reaction. The radicals which may thus besubstituted may include alkyl radicals such as methyl, ethyl, propyl,isopropyl, butyl, isobutyl, amyl, hexyl, heptyl, to octadecyl andhigher; alicyclic radicals such as cyclopentyl, cyclohexyl, etc.; aryland alkaryl radicals such as phenyl, mono-and poly-allql phenyls astolyl, xylyl, mesityl, mono-, di-, and tri-ethyl phenyls, mono-, di-'and triopropyl phenyls, etc.; naphthyl, monoand polyalkyl naphthyls, asmethyl naphthyl, diethyl naphthyl, tripropyl naphthyl, etc.tetrahydronaphthyl; anthracyl, etc.; aralkyl such as benzyl,phenylethyl, etc.; alkenyl such as methallyl, allyl etc.

If the hydrolyzable group or groups of all of the silicanes in themixture to be hydrolyzed are halogens, it is preferable to employ dioxanas the solvent because it is inert to the halogens. If the mixturecontains both halogens and alkoxy groups the former can be converted tothe latter by the slow addition of dry alcohol to the mixture, or themixture can be diluted with dioxan and treated with aqueous alcohol.When the mixture contains only alkoxy groups any water miscible solventmay be used together with a trace of acid such as HCl as catalyst. Inthis case, alcohol may be preferred on account of its relatively lowcost. Mixtures of water miscible solvents may be used.

In the above described method, the slow incor poration of water into thehomogeneous solution ensures that hydrolysis is not permitted to proceedunchecked whereby the. more reactive silicane or silicanes, that is,silicanes containing few or no substituted organic radicals per siliconatom, would be more completely hydrolyzed and condensed before the lessreactive or more highly substituted silicanes have had an opportunity toreact. On the contrary, the less reactive silicanes are thus given agreater opportunity to hydrolyze simultaneously with the more reactivesilicanes than would be the case if the hydrolysis were conductedrapidly. Under these circumstances, simultaneous condensation of thevarious intermediate hydroxy compounds takes place and an intimateintermolecular combination though siloxane linkages of silicon atomsbearing difierent numbers and kinds of organic radicals becomes possibleto the fullest extent. This insures a true inter-condensation with theformation of homogeneous products containing mixed unit structures.

After removal of solvent and excess water the hydrolysis productsresulting from the above pro- .cess are water-immiscible liquids ofvarying viscosity. They are soluble in the common organic solvents suchas benzene, toluene, etc. Many of them are thermoplastic, some arethermosetting, and some are thermally stable liquids. Furthercondensation and polymerization may be brought about by heating, whichgenerally results in an increase in viscosity. The desired degree ofpolymerization will depend largely upon the relative amounts of thevarious types of silicone: initially present.

The various classes of organo-siloxanes which can be produced by mymethod may be represented in the following manner as combinations of thevarious structural units, bearing in mind that the structural units arechemically combined with each other by siloxane linkages, that thepercentage of each type or unit may be varied at will and that theproperties of the resulting products will show corresponding variationswhich can be predicted in making compositions for a particular purpose.In the following clases the formulae corresponding to the structuralunits, exclusive of the oxygen, are

i (RaBl-) (we are I 7 1) i-i e are It is to be understood that the orderin which the structural units of the various organo siloxanes isrepresented has no significance because the units may be Joined in amultiplicity of ways to form chain and cyclic structures andcombinations thereof. Also, the organic radical or radicals in eachstructural unit may be varied in kind.

The partially dehydrated organo siloxanes or hydrolysis products, afterremoval of solvents, are generally liquids of various viscosities andthey vary in the extent to which dehydration has occurred at this stage.Products containing methyl radicals dehydrate more readily than thosecontaining ethyl. propyl, etc., radicals or phenyl radicals and ingeneral products congtaining alkyl radicals dehydrate more readily thanthose containing aryl radicals. The hydrolyzates hereoi dehydrate veryreadily to form the fluids hereof in comparison with hydrolyzates whichhave a higher ratio of oxygen to silicon. The present fluids have anoxygen to silicon atomic ratio of between 0.5 and i. This ratio maylikewise be expressed in terms of the ratio of the number of hydrocarbonradicals to the number of silicon atoms, the equivalent ratio range onthis basis being more than two and less than three. The volatility ofthese fluids decreases with increasing molecular size of the radicalsand at the same time the viscosity may increase somewhat.

The organo siloxanes produced by my method may be adapted to varioususes and for-any meciiic use the physical properties and characteristicsof the product can be controlled by the proper selection oi the initialstartingmaterials so as to obtain the desired oxygen to silicon ratioand a suitable variety of radicals attached to the silicon atom. Theproducts are liquids with little or no tendency for furtherpolymerization even at elevated temperatures and havean oxygen tosilicon ratio between 0.5 and 1.0. Such products have good electricalproperties whereby they may be used as the liquid filling medium fortransformers, circuit breakers. submarine cables, condensers, etc. Ingeneral these products have an unusually low coefiicient of change ofviscosity with temperature and may find use in hydraulic pressuresystems which are subjected to wide changes of temperatures or aslubricants for systems of moving parts operating under subnormal orabnormal temperatures.

The following examples will illustrate the mode of operation of theprocess and the character of the resulting products. In the examples,the starting compound (CeHs)(CHa)aSiC1 was prepared by silicontetrachloride by the action of the phenyl and methyl Grignard reagentsunder substantially anhydrous conditions. distillation of the reactionproduct yielded (CeH5)(CHa)2S1C1 boiling at 79 C. at 15 mm. pressure.The starting compound (CH3) 3Si (OCzHs) was prepared by reactingmethylmagnesium halide with (CHa)aSi(OC2Hs)z under substantiallyanhydrous conditions and fractionally distilling the reaction product torecover the trimethylethoxysilane boiling at 753 C. at 760 mm. pressure.The other starting compounds were prepared in the conventionalmanner, 1. e. by reacting the proper Grignard reagent with eithersilicon tetrachloride, ethyl orthosilicate or organic derivativesthereof in suitable molar ratios and iracticnally. distilling theproduct.

Example 1 Equimolecular parts of (Cal-Is) (CH3)2S1C1 and (CH3)2S1(OC2H5)2 were mixed and treated dropwise with the calculated amountsof water for complete hydrolysis diluted with four volumes of alcohol.On evaporation of solvent a mobile liquid remained which was unchangedby heating and which performed satisfactorily as a transiormer oil.

Composition: O/Si=0.'75.

Example 2 Two equivalents of (Cal-I5) (CH3)S1C12 and one of (CeHs) (CH3)2SiCl were mixed and diluted with dioxan. An amount of water slightly inexcess of the calculated quantity was slowly added. 0n dilution withwater after completion of the inter-condensation, the product wasprecipitated as an oil.

Composition: O/Si=0.83.

Example 3.

2 cc. of anhydrous ethyl alcohol were added to 1 gram oftribenzylsilicon chloride and 8.7 grams of (CH3)'2SI(OC2H5)2. Themixture was allowed to stand for one hour and then an equal volume of a1/1 mixture of concentrated aqueous HCl and ethyl alcohol was added. Themixture was heated and then diluted with water. The product was a.homogeneous oil having useful lubricating properties.

Composition: O/Si==.975.

Fractional I some 95% ethyl alcohol to efiect hydrolysis andintercondensation. Water was then added in slight excess. After boilingoff the solvents. an oily liquid remained.

Composition: /Si=0.83.

Example To a solution of (CeH5.CI-I2)(CeH5)SiCl2 and (CH3)3S1(OC2H5) inthe molar proportions 1/2 was added slowly 95% ethyl alcohol to efiecthydolysis and intercondensation. Water was then added in slight excess.After boiling off the solvents, the concentrated product was a slightlyviscous liquid.

Composition: O/Si=0.67.

Example 6 Example 7 As in the previous example (CH3)2Si(OC2H5)2 and(CH3)3Si(OC2H5) were cohydrolyzed and inter-condensed, except that themolecular pro-' portions were /1 respectively. A liquid prodnet ofsomewhat higher viscosity and boiling range than that in the previousexample was obtained.

Composition: 0/Si=0.95.

Example 8 To a solution of (CsHs-CHzhSiCl and (CH3)2S1(OC2H5)2 in themolar proportions 1/5 was added slowly 95% ethyl alcohol to effect thenadded in slight excess. After boiling oil the solvents, the concentratedproduct was a rather viscous liquid.

Composition: O/Si=().92.

For many uses, particularly in fluid pressure operated devices, it ispreferred to use instead oi the above mixtures of polymers having arange of physical properties, an individual polymer of the specieshaving the definite physical properties of a pure chemical compoundwhere the R's represent the same or different hydrocarbon radicals.These may be obtained by isolation of the individual members from thehydrolysate of a mixture of RaSiX and RzSlXa which is prepared in such amanner as to be substantially completely hydrolyzed and free from cyclicpolymers of the formula (R2SiO)x. This is illustrated by Example 9 whichshows the preparation of a random mixture of polymers belonging to theseries d and the separation of the individual members where n is 1through 13 by distillation under high vacuum.

Example 9.

In a 5 liter three-necked flask, fitted with a reflux condenser,agitator and thermometer, were placed 1393 grams (9.41 mol) ofredistilled (Cl-IslzSflOCfl-B): and 1110 grams (9.41 mol) of (CH3)3S1OC2H5. To this solution was added 254 grams (14.11 mol) of watercontaining 7.5 grams of NaOH, (approximately 1 NaOH per 100 siliconatoms). This insured the formation of only straight chain polymers. Themixture was heated to C. and the temperature continued to rise fornearly an hour. After adding cc. (20% excess) more water, the mixturewas refluxed for 2 hours and then allowed tostand overnight.

Alcohol was then distilled oil, until the temperature reached 100 C.1706.6 grams of distillate was collected. (Theory 1430 grams.) Thisalcohol was poured into four times its volume of water and an insolubleoil separated (457 grams). The insoluble fraction was added back to thecopolymer residue from the distillation and 555 cc. of 20% hydrochloricacid was added. The acid mixture was refluxed for two hours, and thesilicon oils were carefully washed with distilled water until neutral.The yield was 1426 grams (theory 1469 grams).

The oil was distilled in a fractionating column packed with glasshelices, first at atmospheric pressure, then at reduced pressure. Thefractions from the plateaus in the distillation curve were fractionatedand the properties .of' the pure siloxane polymers were determined.These inv dividual fractions are members of the series hydrolysis andinter-condensation. Water was include '(1) the molecular ratio of CH:(CHs):5iO ell-0141mm), i H: where 11:0 to 7 inclusive, that is, thefractions consisted of trimethylsilicyl ether and inter-condensates of(CH3)3SiO with iii. a.

containing from 3 to 9 silicon atoms inclusive. The residue from thefractional distillation was placed in a Claissen flask and distilledunder high vacuum without fractionation. This gave a clear distillatedistilling'over a range of from to 215 C. at 0.125 mm. Refractionationof this distillate showed it to be composed of members of the aboveseries where n is 8 to 13 inclusive. That is, it consisted ofinter-condensates of (CH3)aSiO- with containing from 10 to 15 siliconatoms inclusive. In the preparation of mixtures of molecular specieshaving the general formula -'it is apparent that the average value of nwill depend in general upon several factors which in which one end ofthe polysiloxane chain terminates in a tri-organo-silicyl group and theother terminal Si still contains a hydrolyzable radical. Such moleculescan be converted to poly-siloxanes having both terminal Si atoms bearingthree organic radicals linked by CSi in either of the following ways:(1) continued hydrolysis to replace X with OH and condensation to formor (2) interaction with RaSiOH or (3) conjoint hydrolysis andinter-condensation in the presence of RaSiZ.

Example 10 SiCh and C6H5M82S1Cl were mixed in the molar ratio 1/3. Afterdilution with two volumes of dioxane, aqueous dioxane was added withgreat care. In spite of precautions a considerable amount of silicaprecipitated out showing clearly that satisfactory inter-condensationhad not occurred. n evaporation, however, the liquid portion wassomewhat more viscous than the oil obtained from CaHsMGzSiCl alone. Thisbehavior is undoubtedly due to the wide diiference in reactivity of the$1014 and the trisubstituted halide.

To avoid this dimculty a mixture of halides or the same composition wasagain diluted with dioxane. To this mixture glacial acetic acid was thenadded. There was no sign of precipitation. Some HCl was evolved afteradding a volume of glacial acetic acid approximately equal to theoriginal halide mixture and warming gently, another volume' of aqueousacetic acid (1/3) was added with further warming. On evaporation ofsolvent an oil of medium viscosity resulted. This oil showed no tendencyto body or change with heating at 180 C. for 20 hours.

Composition: (-OSiO-) O/Si=0.87.

I claim:

1. A liquid oopolymeric siloxane of the type where R is an alkenylradical and n has an average value such that the ratio of hydrocarbonradicals to silicon atoms is more than 2 and less than 3.

2. A liquid copolymeric siloxane of the type R! (CH3):[%i O]Si(CHa):

than 3.

JAMES FRANKLIN HYDE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Rochow Oct. 7, 1941 OTHER REFERENCESRochow, Chemistry of the Silicones," 1946, pages 70, '71.

Volnov, "Jour. Gen. Chemistry" (U. 8. S. 1%.), vol. 10 (1940), pages1600-1604.

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